Page 939 - Small Animal Internal Medicine, 6th Edition

CHAPTER 52 Hyperlipidemia 911

TABLE 52.2
VetBooks.ir Effects of Lipemia on Clinical Chemistry Analytes in Canine and Feline Sera* FALSE DECREASE IN VALUES

FALSE INCREASE IN VALUES
CANINE SERA FELINE SERA CANINE SERA FELINE SERA

Total bilirubin Total bilirubin Creatinine Creatinine
Conjugated bilirubin Conjugated bilirubin Total CO 2 Total CO 2
Phosphorus Phosphorus Cholesterol Alanine aminotransferase
Alkaline phosphatase † Alkaline phosphatase † Urea nitrogen
Glucose † Glucose †
Total protein ‡ Total protein ‡
Lipase
Alanine aminotransferase
*Analytes were measured using Coulter DACOS (Coulter Diagnostics, Hialeah, Fla).
† Interference occurs only at very high concentrations of lipid.
‡ When measured using a refractometer.
Adapted from Jacobs RM et al: Effects of bilirubinemia, hemolysis and lipemia on clinical chemistry analytes in bovine, canine, equine and
feline sera, Can Vet J 33:605, 1992.

opaque cream layer over a clear infranatant of serum. If lipase immunoreactivity assay, and low-dose dexamethasone
hypertriglyceridemia is due to excess VLDL particles, the suppression test. A recommendation to treat hyperlipidemia
serum sample will remain turbid. Formation of a cream layer involves a lifelong commitment by the client and therefore
over a cloudy serum layer suggests excess chylomicrons and must not be undertaken lightly. In general, severe hypertri-
VLDL particles. glyceridemia (concentrations > 1000 mg/dL) mandates
Lipoprotein electrophoresis can be used to distinguish the treatment. In this circumstance catabolic mechanisms can be
lipoproteins, and density gradient ultracentrifugation can assumed to be overwhelmed, and the triglyceride concentra-
provide a quantitative measurement of each of the lipopro- tion is very sensitive to a small increase from the intestine
tein classes. However, both of these procedures are time- or the liver. Triglyceride concentrations must be decreased
consuming and are not routinely available for clinical to prevent possible complications, including pancreatitis.
application. The activity of lipoprotein lipase can be assessed In other situations, recommendations will be influenced
by the heparin release test. Serum samples for determination by additional variables, including the underlying disease
of triglyceride concentrations (and, if possible, lipoprotein process. A realistic goal of therapy is to reduce the triglycer-
concentrations) are obtained before and 15 minutes after ide concentration to less than 400 mg/dL, even though such
intravenous administration of heparin (100 IU/kg body a level will still be above the reference interval.
weight in dogs and cats). Heparin causes the release of lipo- Chylomicrons are produced from dietary fat. Therefore
protein lipase from the endothelium and stimulates the restriction of dietary fat relative to the current intake is the
hydrolysis of triglycerides. A defect in lipoprotein lipase is cornerstone of therapy for hypertriglyceridemia. A thorough
suspected if there is no difference between serum triglycer- dietary history should be reviewed, and the diet altered to
ide concentrations before and after administration of one that accomplishes at least a 50% reduction in fat on a
heparin. metabolizable energy (ME) basis. For dogs with moderate to
severe hypertriglyceridemia, the goal is often a diet with less
Treatment than 20% fat on a ME basis (Table 52.3) or lower if the
Before therapy is recommended, every attempt should be patient is already on a lower-fat diet. Nutritional manage-
made to determine whether the hyperlipidemia is primary ment of hypertriglyceridemia in cats is more difficult because
or secondary to an underlying disease process or medication. of the limited availability of diets with less than 25% fat on
Hyperlipidemia secondary to an underlying disorder will an ME basis (Table 52.4). Care should be taken assessing fat
typically resolve or improve with correction of the metabolic content of pet foods. Because the guaranteed analysis
disturbance. Therefore in addition to confirming fasting, reported on pet food labels requires only a minimum, rather
each animal requires a full history, physical examination, than an average, crude fat percentage to be reported, the fat
complete blood count, serum biochemistry panel with thy- content may be significantly higher. In addition, the value is
roxine concentration, and urinalysis. Results of the initial provided on an “as fed” basis, making comparisons among
diagnostic evaluation may indicate the need for additional products challenging. This information is best converted to
diagnostic tests such as abdominal ultrasound, pancreatic and expressed on a ME basis, either as a proportion of